Although recently, several kinds of pharmaceutical composition have been proposed and put into practical use, almost of them exhibit side effects such as leukocytopenia, alopecia and gastrointestinal disturbances. Accordingly, in actual fact, their application is restricted to an extent.
More recently, the application of a substance obtained by chemically bonding an antibody to tumour antigen (hereinafter referred to an anti-tumour-antibody) with an antitumour substance, as an antitumour agent, has been tried. However, since the anti-tumour-antibody used for such a substance is not sufficiently purified, to remove general immunoglobulin and so it could not be recognized as a pure anti-tumour-antibody. Accordingly, in the case where such a substance obtained by bonding such an anti-tumour-antibody with an antitumour substance is administered as an antitumour agent, the occurrence of pyrexia and anaphylactic shock caused by immunoglobulin contained in the above-mentioned anti-tumour-antibody is inevitable.
The inventors taking into consideration of the above-mentioned technical backgrounds have examined the elimination of side effects observed in the use of anti-tumour-antibody and as a result, have confirmed that the extremely pure anti-tumour-antibody is obtained by purifying the immunoglobulin fraction of the antiserum with an affinity-chromatographic technique and that a pharmaceutical composition obtained by bonding the above-mentioned purified antibody to an antitumour substance having at least one amino group or carboxyl group does not exhibit the above-mentioned side effects.
Accordingly, an object of the present invention is to supply a pharmaceutical composition having low cytotoxicity and on the other hand excellent antitumour activity. Also an another object of the present invention is to supply an anti-tumour-antibody with a high purity and a method for preparing the same.